EP0307887B1 - FM-Stereodemodulatoren - Google Patents

FM-Stereodemodulatoren Download PDF

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Publication number
EP0307887B1
EP0307887B1 EP88115018A EP88115018A EP0307887B1 EP 0307887 B1 EP0307887 B1 EP 0307887B1 EP 88115018 A EP88115018 A EP 88115018A EP 88115018 A EP88115018 A EP 88115018A EP 0307887 B1 EP0307887 B1 EP 0307887B1
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EP
European Patent Office
Prior art keywords
stereo
signal
level
output
difference signal
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Expired - Lifetime
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EP88115018A
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English (en)
French (fr)
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EP0307887A2 (de
EP0307887A3 (en
Inventor
Kazuhisa Ishiguro
Mikio Yamagishi
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Sanyo Electric Co Ltd
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Sanyo Electric Co Ltd
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Priority claimed from JP62235442A external-priority patent/JPS6478043A/ja
Priority claimed from JP62331178A external-priority patent/JPH01171335A/ja
Application filed by Sanyo Electric Co Ltd filed Critical Sanyo Electric Co Ltd
Publication of EP0307887A2 publication Critical patent/EP0307887A2/de
Publication of EP0307887A3 publication Critical patent/EP0307887A3/en
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Publication of EP0307887B1 publication Critical patent/EP0307887B1/de
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/06—Receivers
    • H04B1/16—Circuits
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/06—Receivers
    • H04B1/16—Circuits
    • H04B1/1646—Circuits adapted for the reception of stereophonic signals
    • H04B1/1692—Circuits adapted for the reception of stereophonic signals using companding of the stereo difference signal, e.g. FMX

Definitions

  • the present invention relates generally to stereo demodulators for FM stereo broadcasting, and more particularly, to a stereo demodulator which can always keep separation between right and left stereo signals the maximum .
  • a matrix circuit in an FM stereo receiver in which right and left stereo signals are obtained by adding a stereo sum signal to a stereo difference signal levels of the stereo sum signal and the stereo difference signal are adjusted so that good separation is obtained.
  • the adjustment of the levels is made by, for example, the following method.
  • a stereo composite signal including only a left stereo signal and not a right stereo signal is applied to a stereo demodulator, and the level of the stereo sum signal or the stereo difference signal to be applied to the matrix circuit is adjusted by a voltage divider circuit or the like such that an output level of an output terminal for the right stereo signal (right output terminal) of the matrix circuit in the stereo demodulator becomes zero.
  • a voltage divider circuit or the like such that an output level of an output terminal for the right stereo signal (right output terminal) of the matrix circuit in the stereo demodulator becomes zero.
  • a stereo composite signal including only the right stereo signal and not the left stereo signal is applied to the stereo demodulator, and the level of the stereo sum signal or the stereo difference signal is adjusted such that an output level of an output terminal for the left stereo signal (left output terminal) of the matrix circuit becomes zero.
  • right and left stereo signals having good separation can be obtained.
  • Fig. 1 shows a conventional stereo demodulator in which separation is adjusted by adjusting levels of a stereo sum signal and a stereo difference signal applied to a matrix circuit.
  • This stereo demodulator is described in, for example, Japanese Patent Publication No. 15580/1984.
  • a stereo composite signal as FM (frequency-modulation)-detected is applied to an input terminal 101.
  • a stereo sum signal (L+R) in the stereo composite signal is applied to a matrix circuit 104 through a buffer amplifier 102 and an adjusting resistor 103.
  • a stereo difference signal (L-R) in the stereo composite signal is demodulated by a difference signal demodulator 105, so that stereo difference signals (L-R) and -(L-R) whose phases are reverse to each other are applied to the matrix circuit 104.
  • the stereo sum signal (L+R) and the stereo difference signal (L-R) are added so that a left stereo signal L is generated at a left output terminal 106, while the stereo sum signal (L+R) and the stereo difference signal -(L-R) are added so that a right stereo signal R is generated at a right output terminal 107.
  • a series circuit of a variable resistor 108 and a resistor 109 is connected in parallel with the adjusting resistor 103. Separation can be adjusted by adjusting a value of the variable resistor 108.
  • the resistance value of the variable resistor 108 must be manually adjusted while observing waveforms of output signals which appear at the left and right output terminals 106 and 107 of the matrix circuit 104, resulting in the inaccuracy of adjustment and the increase in the number of manufacturing processes.
  • the variable resistor 108 when the stereo demodulator is formed as an integrated circuit, the variable resistor 108 must be externally provided on an IC (integrated circuit), resulting in the increase in the number of parts externally provided and the increase in the number of pins externally provided, which is not preferable.
  • the initialization value of the variable resistor 108 deviates, separation is decreased. Additionally, the resistance value of the variable resistor 108 deviates due to the change in environment such as the change in temperature, the change with time and the change with age, so that the separation is deteriorated again.
  • An object of the present invention is to provide a stereo demodulator which can always keep separation the maximum.
  • Another object of the present invention is to provide a stereo demodulator in which separation is automatically adjusted.
  • Yet still another object of the present invention is to provide a stereo demodulator in which the number of parts externally provided and the number of pins externally provided are not increased when formed as an integrated circuit.
  • a further object of the present invention is to provide a stereo demodulator in which separation is not deteriorated due to the change in environment such as the change in temperature, the change with time and the change with age.
  • the FM stereo demodulator comprises stereo difference signal demodulating means, matrix means, first level detecting means, second level detecting means, first comparing means and first level adjusting means.
  • the stereo difference signal demodulating means demodulates a stereo difference signal in a stereo composite signal.
  • the matrix means generates a left stereo signal and a right stereo signal from a stereo sum signal in the stereo composite signal and the stereo difference signal.
  • the first level detecting means detects a level of the stereo sum signal in the stereo composite signal.
  • the second level detecting means detects a level of the stereo difference signal.
  • the first comparing means compares an output of the first level detecting means with an output of the second level detecting means.
  • the first level adjusting means is responsive to an output of the first comparing means for changing the level of at least one of the stereo sum signal and the stereo difference signal applied to the matrix means, when only either one of the left stereo signal and the right stereo signal is included in the stereo composite signal, such that the outputs of the first level detecting means and the second level detecting means are equal to each other.
  • the levels of the stereo sum signal and the stereo difference signal immediately before application to the matrix means are compared with each other.
  • the first level adjusting means is operated such that the levels of the stereo sum signal and the stereo difference signal coincide with each other, so that separation can be automatically adjusted.
  • the levels of the stereo sum signal and the stereo difference signal can be automatically adjusted.
  • the adjustment work of separation is not completely required.
  • the best separation is always obtained without deviating due to the change in environment, the change with time or the like.
  • An FM stereo demodulator further comprises third level detecting means and switching means.
  • the third level detecting means detects a level of the output of the first comparing means.
  • the switching means applies the output of the first comparing means to the first level adjusting means when an output of the third level detecting means is smaller than a predetermined value while applying a predetermined voltage to the first level adjusting means when the output of the third level detecting means is larger than the predetermined value.
  • An FM stereo demodulator comprises stereo difference signal demodulating means, matrix means, level adjusting means, separation adjusting means, storing means and control signal supplying means.
  • the stereo difference signal demodulating means demodulates a stereo difference signal in a stereo composite signal.
  • the matrix means generates a left stereo signal and the right stereo signal from a stereo sum signal and the stereo difference signal in the stereo composite signal.
  • the level adjusting means changes a level of at least one of the stereo sum signal and the stereo difference signal applied to the matrix means.
  • the separation adjusting means applies a control signal to the level adjusting means, at the time of adjustment of separation, such that separation between the left stereo signal and the right stereo signal generated by the matrix means becomes the maximum.
  • the storing means stores the control signal from the separation adjusting means.
  • the control signal supplying means applies the control signal stored in the storing means to the level adjusting means at the time of reception of stereo broadcasting.
  • the level adjusting means since the level adjusting means is driven in response to the control signal from the separation adjusting means, the levels of the stereo sum signal and the stereo difference signal can exactly coincide with each other, so that the maximum stereo separation can be ensured.
  • the control signal obtained from the separation adjusting means when the maximum stereo separation is obtained is stored in the storing means and the level adjusting means is driven in response to the control signal obtained from the storing means at the time of reception of stereo broadcasting, the stereo demodulator can be always kept in a state in which the maximum separation is always obtained.
  • the stereo demodulator can be obtained which can always keep stereo separation in the best state.
  • the stereo demodulator can be obtained in which separation is not deteriorated due to the change in environment, the change with age or the like.
  • Fig. 2 is a block diagram showing a structure of an FM stereo demodulator according to one embodiment of the present invention.
  • separation is adjusted only when only either one of a left stereo signal and a right stereo signal is included in a stereo composite signal at the time of ordinary reception of FM broadcasting; otherwise separation would not be adjusted.
  • levels of a stereo sum signal (L+R) and a stereo difference signal (L-R) differ from each other.
  • L+R stereo sum signal
  • L-R stereo difference signal
  • an FM detector circuit 1 FM-detects a frequency-modulated stereo composite signal applied to an input terminal 2.
  • a subchannel demodulator (stereo difference signal demodulator) 3 detects a subchannel signal in the stereo composite signal from the FM detector circuit 1 and demodulates a stereo difference signal (L-R).
  • a voltage controlled amplifier (variable gain amplifier) 4 amplifies the stereo difference signal (L-R) obtained from the subchannel demodulator 3.
  • a matrix circuit 5 generates a left stereo signal L and a right stereo signal R from a stereo sum signal (L+R) included in the stereo composite signal from the FM detector circuit 1 and the stereo difference signal (L-R) from the voltage controlled amplifier 4, to output the signals to a left output terminal 13 and a right output terminal 14, respectively.
  • a first low-pass filter 6 eliminates a high frequency component in the stereo sum signal (L+R).
  • a first level detector 7 detects a direct current (dc) voltage corresponding to an output signal of the first low-pass filter 6.
  • a second low-pass filter 8 eliminates a high frequency component in the stereo difference signal (L-R).
  • a second level detector 9 detects a dc voltage corresponding to an output signal of the second low-pass filter 8.
  • An output terminal of a comparator 10 is connected to a smoothing circuit 11 through a switching element 16 and to a level detector 12.
  • the switching element 16 is structured by, for example, transistors.
  • the smoothing circuit 11 smoothes an output signal of the comparator 10 to convert the signal to a dc voltage, to apply the same to the voltage controlled amplifier 4 as a gain control signal.
  • the level detector 12 detects the dc voltage corresponding to the output signal of the comparator 10.
  • a comparator 15 compares an output signal of the level detector 12 with a voltage generated from a voltage source 17, to open the switching element 16 when the output signal of the level detector 12 becomes a voltage of the voltage source 17 or more.
  • the gain of the voltage controlled amplifier 4 is controlled in response to the gain control signal applied from the smoothing circuit 11.
  • Fig. 3 shows a specific embodiment of each of the first level detector 7, the second level detector 9 and the level detector 12.
  • the level detector shown in Fig. 3 is a diode detector, which comprises a diode D1 and a capacitor C1.
  • the first level detector 7, the second level detector 9 and the level detector 12 may have another structures in which a level of an alternating current signal can be detected. For example, they may be a full-wave rectifier.
  • Fig. 4 shows a specific example of the smoothing circuit 11.
  • the smoothing circuit comprises resistors R1 and R2 and a capacitor C2.
  • the resistance value of the resistor R1 is small while the resistance value of the resistor R2 is large. Consequently, the charging time constant becomes small while the discharging time constant becomes large. Therefore, even if the charging time is short, an output voltage can be held for a long time.
  • a frequency-modulated stereo composite signal applied to the input terminal 2 is FM-detected in the FM detector circuit 1, to be applied to the matrix circuit 5 and the subchannel demodulator 3.
  • the subchannel demodulator 3 a subchannel signal in the stereo composite signal is demodulated, so that a stereo difference signal (L-R) is obtained.
  • the stereo difference signal (L-R) is applied to the matrix circuit 5 through the voltage controlled amplifier 4.
  • the gain of the voltage controlled amplifier 4 is controlled such that the level of the stereo difference signal (L-R) is raised. Consequently, the stereo sum signal (L+R) and the stereo difference signal (L-R) whose respective levels are automatically adjusted are applied to the matrix circuit 5. As a result, the left stereo signal L and the right stereo signal R correctly separated from each other are outputted from the left output terminal 13 and the right output terminal 14 of the matrix circuit 5, respectively.
  • the level difference between the stereo sum signal (L+R) and the stereo difference signal (L-R) is small. Therefore, the level of the output signal of the comparator 10 is lower than a voltage level of the voltage source 17. Thus, the switching element 16 is kept in a closed state. More specifically, the gain of the voltage controlled amplifier 4 is controlled in response to the gain control signal applied from the comparator 10 through the smoothing circuit 11.
  • the left stereo signal L and the right stereo signal R have the same level and reverse in phase to each other.
  • the level of the stereo sum signal (L+R) becomes zero
  • a level of the signal applied to the negative input terminal of the comparator 10 also becomes zero. Consequently, the level difference between the signals respectively applied to the positive input terminal and the negative input terminal of the comparator 10 becomes large, so that a gain control signal at a higher level than the voltage level of the voltage source 17 is outputted from the output terminal of the comparator 10.
  • a control signal is applied to the switching element 16 from the output terminal of the comparator 15. The switching element 16 enters an opened state in response to the control signal.
  • the gain control signal outputted from the comparator 10 is not applied to the voltage controlled amplifier 4.
  • a voltage held in the capacitor C2 in the smoothing circuit 11 before the switching element 16 is opened continues to be applied to the voltage controlled amplifier 4 as a gain control signal.
  • the levels of the stereo sum signal (L+R) and the stereo difference signal (L-R) are kept in the optimum state adjusted when only either one of the right stereo signal R and the left stereo signal L are received.
  • the right stereo signal R and the left stereo signal L have the same level and are in phase with each other.
  • the level of the stereo difference signal (L-R) becomes zero, the level of the signal applied to the positive input terminal of the comparator 10 becomes zero. Consequently, the level difference between the signals respectively applied to the negative input terminal and the positive input terminal of the comparator 10 becomes large, so that a gain control signal at a lower level than the bias voltage of the comparator 10 is outputted from the output terminal of the comparator 10. Therefore, the low level gain control signal is applied to the voltage controlled amplifier 4 through the smoothing circuit 11, so that the gain of the voltage controlled amplifier 4 is increased.
  • the level of the stereo difference signal is zero, a voltage is not applied to the input terminal of the voltage controlled amplifier 4. Consequently, even if the gain of the voltage controlled amplifier 4 is increased, the stereo difference signal (L-R) is not outputted from the output terminal thereof.
  • the gain of the voltage controlled amplifier 4 must be limited such that there is no effect of the noises. More specifically, it is necessary that an amplifier having too large gain is not employed as the voltage controlled amplifier 4.
  • Fig. 5 shows another example of the circuit portion for applying the gain control signal to the voltage controlled amplifier 4.
  • a switching element 18 and a voltage source 19 are provided instead of the switching element 16 shown in Fig. 2.
  • the switching element 18 is switched to the side of a contact a; otherwise it is switched to the side of a contact b.
  • a constant voltage is applied to the voltage controlled amplifier 4 from the voltage source 19 as a gain control signal. Therefore, the gain of the voltage controlled amplifier 4 is set constant.
  • the voltage controlled amplifier 4 is provided in a signal path of the stereo difference signal (L-R)
  • the voltage controlled amplifier 4 may be provided in a signal path of the stereo sum signal (L+R) so that the level of the stereo sum signal (L+R) is adjusted.
  • the voltage controlled amplifier 4 may be provided in the preceding stage of the subchannel demodulator 3.
  • Fig. 6 is a block diagram showing a structure of an FMX stereophonic broadcasting receiver to which the present invention is applied.
  • a transmission signal of the FMX broadcasting includes a stereo difference signal (L-R)′ as level-compressed and phase-shifted, by 90°, from a stereo difference signal (L-R), which is broadcast simultaneously with a transmission signal of the conventional FM stereo broadcasting, for example, a stereo sum signal (L+R) and a stereo difference signal (L-R). Therefore, in the stereo broadcasting receiver, the compressed stereo difference signal (L-R)′ must be expanded.
  • a stereo sum signal M, a stereo difference signal S and a compressed stereo difference signal S′ are demodulated, to be outputted from terminals 37, 38 and 39, respectively.
  • the compressed stereo difference signal S′ outputted from the receiving circuit 36 is added to the stereo difference signal S outputted from the receiving circuit 36 in an adder 20.
  • a level of a signal (S+S′) obtained by addition is expanded in an expander 21 such that the level is equal to a level of the stereo difference signal S.
  • the stereo sum signal M outputted from the receiving circuit 36 is directly applied to a matrix circuit 5.
  • the stereo difference signal S is applied to the matrix circuit 5 through a first voltage controlled amplifier 22 and a switch 23.
  • the output signal (S+S′) of the expander 21 is applied to the matrix circuit 5 through the second voltage controlled amplifier 24 and the switch 23.
  • the receiving circuit 36 contains a determining circuit for determining whether or not a reception signal is a broadcasting signal of the FMX stereophonic broadcasting.
  • the switch 23 is switched to the side of a contact c in response to a control signal outputted from the receiving circuit 36, as shown in Fig. 6.
  • This state is the same as the state in which the FM stereo demodulator shown in Fig. 2 receives the FM stereo broadcasting.
  • an output signal corresponding to the level difference between the stereo sum signal M and the stereo difference signal S is generated at an output terminal of a first comparator 25.
  • the output signal of the first comparator 25 is smoothed in a first smoothing circuit 26 and then, applied to the first voltage controlled amplifier 22 as a gain control signal. Consequently, the gain of the first voltage controlled amplifier 22 is controlled such that the level of the stereo difference signal S outputted from the first voltage controlled amplifier 22 is equal to the level of the stereo sum signal M.
  • the switch 23 is switched to the side of a contact d in response to the control signal outputted from the receiving circuit 36.
  • the output signal (S+S′) of the expander 21 is applied to the matrix circuit 5 through the second voltage controlled amplifier 24 and the switch 23.
  • a high frequency component of an output signal of the second voltage controlled amplifier 24 is removed in a third low-pass filter 27 and then, the output signal is level-detected in a third level detector 28, to be converted to a dc voltage.
  • the dc voltage outputted from the third level detector 28 is compared with a dc voltage outputted from a first level detector 7 in a second comparator 29, so that an output voltage corresponding to the level difference therebetween is outputted from the second comparator 29.
  • the output signal of the second comparator 29 is smoothed by a second smoothing circuit 30 and then, applied to the second voltage controlled amplifier 24 as a gain control signal. Consequently, the gain of the second voltage controlled amplifier 24 is controlled such that a level of the output signal (S+S′) of the second voltage controlled amplifier 24 is equal to the level of the stereo sum signal M.
  • a circuit comprising a first level detector 31a, a comparator 32a, a switching element 33a and a voltage source 34a and a circuit comprising a second level detector 31b, a comparator 32b, a switching element 33b and a voltage source 34b are the same as that of a circuit comprising the level detector 12, the comparator 15, the switching element 16 and the voltage source 17 shown in Fig. 2. More specifically, when the stereo broadcasting signal including only either one of the left stereo signal L and the right stereo signal R is received, the switching element 33a or 33b is closed, so that the output signal of the first or second comparator 25 or 29 is applied to the first or second voltage controlled amplifier 22 or 24 as a gain control signal.
  • the switching element 33a or 33b is opened, so that a voltage held in the first or second smoothing circuit 26 or 30 immediately before continues to be applied to the first or second voltage controlled amplifier 22 or 24 as a gain control signal.
  • Fig. 7 is a block diagram showing a structure of an FM stereo demodulator according to another embodiment of the present invention.
  • a stereo composite signal as FM-detected is applied to an input terminal 41.
  • a stereo sum signal (L+R) in the stereo composite signal is applied to a matrix circuit 44 through a buffer amplifier 42.
  • a stereo difference signal (L-R) in the stereo composite signal is demodulated in a difference signal demodulator 45, so that a first stereo difference signal (L-R) and a second stereo difference signal -(L-R) whose phases are reverse to each other are outputted.
  • a first voltage controlled amplifier 50 controls a level of the first stereo difference signal (L-R) outputted from the difference signal demodulator 45, to apply the same to the matrix circuit 44.
  • a second voltage controlled amplifier 51 controls a level of the second stereo difference signal -(L-R) outputted from the difference signal demodulator 45, to apply the same to the matrix circuit 44.
  • the matrix circuit 44 generates a left stereo signal L by adding the stereo sum signal (L+R) to the first stereo difference signal (L-R), to output the same from a left output terminal 46.
  • the matrix circuit 44 generates a right stereo signal R by adding the stereo sum signal (L+R) to the second stereo difference signal -(L-R), to output the same to a right output terminal 47.
  • a first switch 52 selects either one of the left stereo signal L outputted from the left output terminal 46 and the right stereo signal R outputted from the right output terminal 47, to output the same.
  • a separation adjusting circuit 53 comprises a low-pass filter 54, a detector 55 and a comparator 56.
  • the low-pass filter 54 eliminates a high frequency component of the output signal of the first switch 52.
  • the detector 55 detects an output signal of the low-pass filter 54.
  • the comparator 56 compares an output signal of the detector 55 with a reference voltage applied from a voltage source 56a.
  • An output signal of the comparator 56 is applied to the first voltage controlled amplifier 50 through a second switch 57 as a gain control signal.
  • the output signal of the comparator 56 is applied to the second voltage controlled amplifier 51 through a third switch 58 as a gain control signal.
  • the output signal of the comparator 56 is applied to a holding circuit 60 through a fourth switch 59. Meanwhile, a voltage generated from the voltage source 56a is equal to an output bias voltage of the detector 55.
  • the holding circuit 60 holds the output signal applied from the comparator 56 through the fourth switch 59.
  • An A-D converter 61 A-D (analog-digital) converts the output signal of the holding circuit 60.
  • a digital signal outputted from the A-D converter 61 is applied to a first memory 64 through a fifth switch 62.
  • the first memory 64 stores the digital signal applied from the A-D converter 61.
  • the digital signal outputted from the A-D converter 61 is applied to a second memory 66 through a sixth switch 63.
  • the second memory 66 stores the digital signal applied from the A-D converter 61.
  • a first D-A converter 65 D-A (digital-analog) converts the digital signal stored in the first memory 64, to apply the same to the first voltage controlled amplifier 50 as a gain control signal.
  • a second D-A converter 67 D-A converts the digital signal stored in the second memory 66, to apply the same to the second voltage controlled amplifier 51 as a gain control signal.
  • the first switch 52 is switched to the side of a contact l, the second switch 57 is turned on, and the third to sixth switches 58, 59, 62 and 63 are turned off.
  • a stereo composite signal including only a component of the right stereo signal R is applied to the input terminal 41. Consequently, the separation adjusting circuit 53 comprising the low-pass filter 54, the detector 55 and the comparator 56 is operated, so that the gain of the first voltage controlled amplifier 50 is adjusted such that leakage of the right stereo signal R applied to the low-pass filter 54 from the left output terminal 46 through the first switch 52 becomes zero.
  • a level of the first stereo difference signal (L-R) is adjusted by the first voltage controlled amplifier 50 such that a level of the output signal of the detector 55 is equal to a voltage level of the voltage source 56a.
  • the fourth and fifth switches 59 and 62 are turned on, and the second switch 57 is turned off. Consequently, the gain control signal outputted from the comparator 56 is applied to the holding circuit 60 through the fourth switch 59, to be A-D converted by the A-D converter 61.
  • the digital signal outputted from the A-D converter 61 is stored in the first memory 64.
  • the first switch 52 is switched to the side of a contact r, the third switch 58 is turned on, and the other switches 57, 59, 62 and 63 are turned off. Furthermore, the stereo composite signal including only a component of the left stereo signal L is applied to the input terminal 41. Consequently, the separation adjusting circuit 53 is operated, so that a level of the second stereo difference signal -(L-R) is adjusted by the second voltage controlled amplifier 51 such that leakage of the left stereo signal L applied to the low-pass filter 54 from the right output terminal 47 through the first switch 52 becomes zero. Thereafter, the first and sixth switches 59 and 63 are turned on, and the third switch 58 is turned off.
  • the gain control signal outputted from the comparator 56 is applied to the holding circuit 60 through the fourth switch 59, to be A-D converted by the A-D converter 61.
  • the digital signal outputted from the A-D converter 61 is stored in the second memory 66.
  • the levels of the first stereo difference signal (L-R) and the second stereo difference signal-(L-R) are adjusted such that stereo separation becomes the maximum by suitably switching the first to sixth switches 52, 57, 58, 59, 62 and 63, so that data concerning the gain control signals applied to the first and second voltage controlled amplifiers 50 and 51 at the time of adjustment are stored in the first and second memories 64 and 66.
  • the first and second D-A converters 65 and 67 are kept in a reset state in response to a reset signal RST.
  • the reset state of the first and second D-A converters 65 and 67 is released.
  • the first and second memories 64 and 66 are structured by a nonvolatile memory, a memory with back-up power supply or the like such that stored data does not disappear even if the power supply of the FM stereo broadcasting receiver is disconnected.
  • the second to sixth switches 57, 58, 59, 62 and 63 are all turned off. Consequently, when FM stereo broadcasting is being received, the first and second voltage controlled amplifiers 50 and 51 are controlled in accordance with the data stored in the first and second memories 64 and 66. More specifically, the data stored in the first and second memories 64 and 66 are D-A converted by the first and second D-A converters 65 and 67, so that analog signals obtained by D-A conversion are applied to the first and second voltage controlled amplifiers 50 and 51 as gain control signals.
  • the levels of the output signals of the first and second voltage controlled amplifiers 50 and 51 become values determined by adjusting the above described stereo separation, respectively, so that separation between the left and right stereo signals L and R outputted from the left and right output terminals 46 and 47 of the matrix circuit 44 becomes the maximum.
  • a microcomputer has been employed in various portions such as a tuning circuit portion and a function switching circuit portion.
  • the first to sixth switches may be switched by a person.
  • the first to sixth switches may be switched by a microcomputer. In this case, stereo separation is automatically adjusted.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Stereo-Broadcasting Methods (AREA)

Claims (15)

  1. Ein FM-Stereo-Demodulator zum Demodulieren eines linken Stereosignals und eines rechten Stereosignals aus einem zusammengesetzten Stereosignal, das als Frequenzmodulation detektiert worden ist, und ein Stereo-Summensignal und ein Stereo-Differenzsignal enthält, bestehend aus:
    einer Stereo-Differenzsignal-Demodulator-Einrichtung (3) zum Demodulieren des Stereo-Differenzsignals des zusammengesetzten Stereosignals,
    einer Matrixeinrichtung (5) zum Erzeugen des linken und rechten Stereosignals aus dem Stereo-Summensignal des zusammengesetzten Stereosignals und dem Stereo-Differenzsignal von der Stereo-Differenzsignal-Demodulator-Einrichtung (3);
    gekennzeichnet durch:
    erste Pegel-Detektormittel (7) zum Detektieren eines Pegels des Stereo-Summensignals im zusammengesetzten Stereosignal, zweite Pegel-Detektormittel (9) zum Detektieren eines Pegels des Stereo-Differenzsignals von der Stereo-Differenzsignal-Demodulatoreinrichtung (3),
    eine erste Vergleichereinrichtung (10) zum Vergleichen eines Ausgangs an den ersten Pegel-Detektormittel (7) mit einem Ausgang der zweiten Pegel-Detektormittel (9) und eine erste Pegel-Einstelleinrichtung (4), die auf einen Ausgang der ersten Vergleichereinrichtung (10) anspricht, um den Pegel von wenigstens einem von Stereosummensignal und Stereodifferenzsignal, das an die Matrixeinrichtung (5) angelegt wird, zu ändern, wenn nur eines der rechten und linken Stereosignale im zusammegesetzten Stereosignal enthalten ist, so daß der Ausgang der ersten Pegel-Detektormittel (7) gleich dem Ausgang der zweiten Pegel-Detektormittel (9) ist.
  2. FM-Stereo-Demodulator nach Anspruch 1,
    weiterhin gekennzeichnet durch:
    dritter Pegel-Detektormittel (12) zum Detektieren eines Pegels des Ausgangs der ersten Vergleichereinrichtung (10), und
    erste Schaltmittel (16), die den Ausgang der ersten Vergleichereinrichtung (10) an die erste Pegel-Einstelleinrichtung (4) anlegen, wenn ein Ausgang der dritten Pegel-Detektormittel (12) kleiner als ein vorbestimmter Wert ist, wobei an die erste Pegeleinstell-Einrichtung (4) eine vorbestimmte Spannung angelegt wird, wenn der Ausgang der dritten Pegel-Detektormittel (12) größer als der vorbestimmte Wert ist.
  3. FM-Stereo-Demodulator nach Anspruch 2,
    weiterhin gekennzeichnet durch:
    eine Glättungseinrichtung (11) zum Glätten des Ausgangs der ersten Vergleichereinrichtung (10), wobei die ersten Schaltmittel aufweisen
    eine zweite Vergleichereinrichtung (15) zum Vergleichen des Ausgangs der dritten Pegel-Detektormittel (12) mit dem vorbestimmten Wert, und
    ein Schaltelement (16), das zwischen die erste Vergleichereinrichtung und die Glättungseinrichtung (11) geschaltet ist, und das darauf anspricht, ob ein Ausgang der zweiten Vergleichereinrichtung (15) leitend oder nicht leitend wird.
  4. FM-Stereo-Demodulator nach Anspruch 3,
    dadurch gekennzeichnet, daß die Glättungseinrichtung (11) eine kurze Ladezeitkonstante und eine lange Entladezeitkonstante hat.
  5. FM-Stereo-Demodulator nach Anspruch 2,
    weiter gekennzeichnet durch:
    eine Glättungseinrichtung (11) zum Glätten des Ausgangs der ersten Vergleichereinrichtung (10),
    wobei die ersten Schaltmittel aufweisen:
    eine zweite Vergleichereinrichtung (15) zum Vergleichen des Ausgangs der dritten Pegel-Detektormittel (12) mit dem vorbestimmten Wert,
    eine Spannungsquelle (19) zum Erzeugen einer vorbestimmten Spannung, und
    ein Schaltelement (18), das auf den Ausgang der zweiten Vergleichereinrichtung (15) anspricht, um wahlweise an die erste Pegeleinstelleinrichtung (4) einen Ausgang der Glättungseinrichtung (11) oder die vorbestimmte Spannung, die durch die Spannungsquelle (19) erzeugt wird, anzulegen.
  6. FM-Stereo-Demodulator nach Anspruch 1,
    weiterhin gekennzeichnet durch:
    ein erstes Niederpaßfilter (6) zum Entfernen einer Hochfrequenzkomponente aus dem Stereo-Summensignal, das an die ersten Pegeldetektormittel (7) angelegt wird, und ein zweites Niederpaßfilter (8) zum Entfernen einer Hochfrequenzkomponente aus dem Stereo-Differenzsignal, das an die zweiten Pegeldetektormittel (9) angelegt wird.
  7. FM-Stereo-Demodulator nach Anspruch 1,
    dadurch gekennzeichnet, daß die erste Pegeleinstell-Einrichtung einen spannungsgesteuerten Verstärker (4) aufweist.
  8. FM-Stereo-Demodulator nach Anspruch 1,
    dadurch gekennzeichnet, daß das zusammengesetzte Stereosignal weiterhin ein Stereo-Differenzsignal als verdichteter Pegel aufweist, und weiterhin vorgesehen ist eine verdichtete Stereo-Differenzsignal-Demodulatoreinrichtung (36) zum Demodulieren des Stereo-Differenzsignals als verdichteter Pegel, im zusammengesetzten Stereosignal;
    eine Addiereinrichtung (20), um das Stereo-Differenzsignal dem verdichteten Stereo-Differenzsignal zu addieren,
    eine Ausdehneinrichtung (21) zum Ausdehnen eines Ausgangs der Addiereinrichtung (20),
    vierte Pegel-Detektormittel (28) zum Detektieren eines Pegels eines Signals, das an der Ausdehneinrichtung (21) ausgegeben worden ist,
    eine dritte Vergleichereinrichtung (29) zum Vergleichen des Ausgangs der ersten Pegel-Detektormittel (7) mit einem Ausgang der vierten Pegel-Detektormittel (28),
    eine zweite Pegeleinstelleinrichtung (24), die auf einen Ausgang der dritten Vergleichereinrichtung (29) anspricht, um den Pegel des Signals, das an der Ausdehneinrichtung (21) ausgegeben wird, wenn nur eines, das linke oder rechte Stereosignal im zusammengesetzten Stereosignal enthalten ist, so zu ändern, daß der Ausgang der ersten Pegel-Detektormittel (7) gleich dem Ausgang der vierten Pegel-Detektormittel (28) ist, und
    zweite Schaltmittel (33b) zum wahlweisen Anlegen eines Ausgangs der ersten Regeleinstell-Einrichtung (22) oder eines Ausgangs der zweiten Pegeleinstelleinrichtung (24) an die Matrixeinrichtung (5).
  9. FM-Stereo-Demodulator zum Demodulieren eines linken Stereosignals und eines rechten Stereosignals aus einem zusammengesetzten Stereosignal, das als Frequenzmodulation detektiert worden ist, welches ein Stereo-Summensignal und ein Stereo-Differenzsignal enthält, mit:
    einer Stereo-Differenzsignal-Demoduliereinrichtung (45) zum Demodulieren des Stereo-Differenzsignals in dem zusammengesetzten Stereosignal,
    einer Matrixeinrichtung (44) zum Erzeugen des linken Stereosignals und des rechten Stereosignals aus dem Stereosummensignal im zusammengesetzten Stereosignal und dem Stereo-Differenzsignal von der Stereo-Differenzsignal-Demodulator-Einrichtung (45),
    gekennzeichnet durch:
    eine Pegeleinstelleinrichtung (50, 51), um einen Pegel von wenigstens einem Signal, dem Stereo-Summensignal und dem Stereo-Differenzsignal, das an die Matrixeinrichtung (44) angelegt werden soll, zu ändern;
    eine Trenneinstelleinrichtung (53), die an die Pegeleinstell-Einrichtung (50, 51) zum Zeitpunkt der Einstellung der Stereotrennung ein Steuersignal so anlegt, daß die von der Matrixeinrichtung (44) erhaltene Trennung zwischen dem linken Stereosignal und dem rechten Stereosignal, das Maximum ist,
    Speichermittel (64, 66) zum Speichern des Steuersignals der Trenneinrichtung (53) und
    eine Steuersignal-Zuführeinrichtung (65, 66, 67) zum Anlegen des in den Speichermitteln (64, 66) gespeicherten Steuersignals an die Pegeleinstell-Einrichtungen (50, 51) zum Zeitpunkt des Empfangs einer stereophonen Rundfunksendung.
  10. FM-Stereo-Demodulator nach Anspruch 9,
    dadurch gekennzeichnet, daß
    die Matrixeinrichtung (44) jeweils für das linke Stereosignal und für das rechte Stereosignal Ausgangsklemmen (46, 47) aufweist, und
    daß die Trenneinstelleinrichtung (53) das Steuersignal so an die Pegeleinstelleinrichtung (50, 51) anlegt, daß wenn ein zusammengesetztes Stereosignal, das nur eines der linken und rechten Stereosignale enthält, angelegt ist, der Pegel eines Signals Null wird, das an einer Ausgangsklemme (46, 47) erscheint, an welcher das andere der linken und rechten Stereosignale ausgegeben wird.
  11. FM-Stereo-Demodulator nach Anspruch 10,
    dadurch gekennzeichnet, daß die Trenneinstell-Einrichtung aufweist
    Pegeldetektormittel (55) zum Detektieren der Pegel der Signale, die an den Ausgangsklemmen (46, 47) der Matrixeinrichtung (44) erscheinen,
    erste Schaltmittel (52) zum selektiven Anschließen einer der Ausgangsklemmen (46, 47) der Matrixeinrichtung (44) an die Pegel-Detektormittel (55), eine Vergleichereinrichtung (56) zum Vergleichen eines Ausgangs der Pegel-Detektormittel (55) mit einer vorbestimmten Spannung, und
    zweite Schaltmittel (57, 58) zum selektiven Anschließen oder Abschalten der Vergleichereinrichtung (56) und der Pegeleinstelleinrichtung (50, 51).
  12. FM-Stereo-Demodulator nach Anspruch 11,
    dadurch gekennzeichnet, daß die Speichermittel aufweisen
    eine A-D-Konvertereinrichtung (61) zum analogen/digitalen Umwandeln des Steuersignals von der Trenneinstell-Einrichtung (53),
    dritte Schaltmittel (59) zum selektiven Anschließen oder Abschalten der Trenneinstelleinrichtung (53) und der A-D-Konvertereinrichtung,
    Speichermittel (64, 66) zum Speichern eines Ausgangs der A-D-Konvertereinrichtung (61),
    vierte Schaltmittel (62, 63), zum selektiven Anschließen oder Abschalten der A-D-Konvertereinrichtung (61) und der Speichermittel (64, 66) und
    eine D-A-Konvertereinrichtung (65, 67) zum digitalen/ analogen Umwandeln des Ausgangs der Speichermittel (64, 66).
  13. FM-Stereo-Demodulator nach Anspruch 12,
    dadurch gekennzeichnet, daß
    die Stereo-Differenzsignal-Demodulatoreinrichtung (45) auf das zusammengesetzte Stereosignal anspricht, um ein erstes Stereo-Differenzsignal und ein zweites Stereo-Differenzsignal mit zur Polarität des ersten Stereo-Differenzsignals umgekehrter Polarität, auszugeben,
    wobei die Pegeleinstelleinrichtung eine erste Pegeleinstelleinrichtung (50) zum Ändern eines Pegels des ersten Stereo-Differenzsignals und eine zweite Pegeleinstell-Einrichtung (51) zum Ändern eines Pegels des zweiten Stereo-Differenzsignals aufweist,
    wobei die zweiten Schaltmittel einen ersten Schalter (57), der zwischen Vergleichereinrichtung (56) und erster Pegeleinstelleinrichtung (50) geschaltet ist, und einen zweiten Schalter, der zwischen Vergleichereinrichtung (56) und zweiter Pegeleinstelleinrichtung (51) geschaltet ist, aufweist,
    wobei die Speichermittel einen ersten Speicher (64) zum Speichern des Steuersignals entsprechend der ersten Pegeleinstell-Einrichtung (50) und einen zweiten Speicher (66) zum Speichern des Steuersignals entsprechend der zweiten Pegeleinstell-Einrichtung (51), aufweist, und
    die D-A-Konvertereinrichtung einen dem ersten Speicher (64) entsprechenden ersten D-A-Konverter (65) und einen dem zweiten Speicher (66) entsprechenden zweiten D-A-Konverter (67) hat.
  14. FM-Stereo-Demodulator nach Anspruch 11,
    weiterhin gekennzeichnet durch:
    ein Niederpaß-Filter (54) zum Entfernen der entsprechenden Hochfrequenzkomponenten aus den Signalen, die auf die Ausgangsklemmen (46, 47) in der Matrixeinrichtung (44) ausgegeben werden.
  15. Stereo-Demodulator zum Demodulieren eines linken Stereosignals und eines rechten Stereosignals eines zusammengesetzten Stereosignals, das als Frequenzmodulation detektiert worden ist, und ein Stereo-Summensignal und ein Stereo-Differenzsignal hat, mit
    einer Stereo-Differenzsignal-Demoduliereinrichtung (3; 45) zum Demodulieren des Stereo-Differenzsignals im zusammengesetzten Stereosignal;
    einer Matrixeinrichtung (5; 44) zum Erzeugen des linken Stereosignals und des rechten Stereosignals aus dem Stereo-Summensignal im zusammengesetzten Stereosignal und dem Stereo-Differenzsignal von der Stereo-Differenzsignal-Demoduliereinrichtung (3; 45),
    gekennzeichnet durch
    eine Pegeleinstell-Einrichtung (4; 50, 51) zum Ändern eines Pegels von wenigstens einem des Stereo-Summensignals und des Stereo-Differenzsignals, das an die Matrixeinrichtung (5; 44) angelegt werden soll, und
    eine Trenneinstell-Einrichtung (7, 9, 10; 53) zum Versorgen der Pegeleinstelleinrichtung (4; 50, 51) mit einem Steuersignal so, daß die Trennung des linken Stereosignals und des rechten Stereosignals, die durch die Matrixeinrichtung (5; 44) erhalten wird, das Maximum wird.
EP88115018A 1987-09-18 1988-09-14 FM-Stereodemodulatoren Expired - Lifetime EP0307887B1 (de)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
JP235442/87 1987-09-18
JP62235442A JPS6478043A (en) 1987-09-18 1987-09-18 Fm stereoscopic demodulation circuit
JP62331178A JPH01171335A (ja) 1987-12-25 1987-12-25 ステレオ復調回路の分離度調整装置
JP331178/87 1987-12-25

Publications (3)

Publication Number Publication Date
EP0307887A2 EP0307887A2 (de) 1989-03-22
EP0307887A3 EP0307887A3 (en) 1990-06-06
EP0307887B1 true EP0307887B1 (de) 1994-01-12

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EP (1) EP0307887B1 (de)
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US9654885B2 (en) 2010-04-13 2017-05-16 Starkey Laboratories, Inc. Methods and apparatus for allocating feedback cancellation resources for hearing assistance devices
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DE3887049T2 (de) 1994-05-05
EP0307887A2 (de) 1989-03-22
DE3887049D1 (de) 1994-02-24
KR970000160B1 (ko) 1997-01-04
KR890005970A (ko) 1989-05-18
US4972482A (en) 1990-11-20
EP0307887A3 (en) 1990-06-06

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